The present invention relates generally to heat dissipative apparatus for electrical circuitry, and, more particularly, to a heat sink which may be assembled in-line with an electrical circuit during assembly thereof.
A byproduct of normal operation of an electrical circuit is thermal energy, i.e., heat. Thermal energy is generated as a result of frictional effects of charge flow during operation of the electrical circuit. Greater charge flows i.e., larger currents, generate greater amounts of thermal energy. If not dissipated, a buildup of thermal energy can cause abnormal operation of the electrical circuit, and can even cause damage to the component elements of the electrical circuit, as well as component elements of other circuits positioned proximate to the component elements.
Generation of thermal energy is particularly significant in amplification elements such as, for example, a power amplifier. Because an amplification element amplifies the values of signals supplied thereto, signals output by the amplification element are oftentimes many times the levels of the signals supplied to the element. However, the efficiency of a typical amplification element is only about 60%; therefore, about 40% of any signal supplied to the amplification element is not amplified, but, rather, is converted into thermal energy. In order to prevent damage from occurring to the amplification element (as well as other component elements positioned proximate thereto), means for dissipating the generated thermal energy is oftentimes positioned in close physical proximity to the amplification element. More particularly, heat sinks comprised of thermally conductive materials are oftentimes positioned directly above the amplification element and a thermally conductive path is created between the element and the heat sink to permit thermal energy contained in, or generated during operation of, the amplification element to be conducted to the heat sink whereat the thermal energy is dissipated by convection.
Heat sinks for other electrical circuit component elements are similarly utilized. For example, heat sinks for several small circuit component elements are available which may merely be clipped or otherwise pressed into position upon the element in order to provide a convective surface whereat heat generated by or contained in the circuit element may be dissipated. For example, E G & G WAKEFIELD ENGINEERING OF Wakefield, Mass. markets a series 298 "pressed top heat sink". This heat sink may be pressed onto a discrete transistor housing and consists of a convective surface and a connecting means comprised of a thermally conductive material to conduct thermal energy away from the transistor to be dissipated by the convective surface. However, no similar heat sink is available for dissipating heat contained in, or generated by, larger circuits.
Existing heat sink apparatus for amplification elements, and other large circuit component elements, comprise an assembly which is affixed to the amplification element. In order to create a thermally conductive path which permits conduction of thermal energy away from the amplification element, a substantial portion of the surface of the element must be maintained in physical abutment with a thermally conductive material comprising a portion of the heat sink assembly to permit conduction of thermal energy thereaway. In order to maintain such physical abutment, these existing heat sink assemblies require threaded shaft members to provide a clamping force for maintaining the thermally conductive material in the physical abutment with the surface of the element. The thermally conductive material provides a thermal conductive path to a convective surface formed by the heat sink assembly.
Such a heat sink assembly is not be assembled in-line during assembly of the electrical circuit, typically disposed upon a circuit board, of which the amplification element, or other circuit component element, forms a portion. Rather, the heat sink and the circuit component is assembled theretogether during a subassembly process, and, only once assembled may the entire subassembly be assembled in-line during assembly of the electrical circuit.
The requirement of a separate subassembly process increases production costs significantly. What is needed, therefore, is a heat sink assembly for a circuit element which may be constructed in-line during assembly of the electrical circuit.
Normal operation of an electrical circuit containing a high frequency oscillator causes generation of high frequency electromagnetic signals. These electromagnetic signals are undesirable as the generated signals can interfere with normal functioning of other electrical circuits. In order to minimize the deleterious effects of such radio frequency electromagnetic signals, electromagnetic shielding materials are oftentimes positioned to cover discrete circuit elements, or even entire electrical circuits. Such shielding materials not only prevent the transmission of the radio frequency electromagnetic signals generated by the electrical circuit over which the shielding material is positioned, but, further, the shielding material shields the circuit elements and/or circuits to prevent transmission of the radio frequency electromagnetic signals generated by other electrical circuits thereto.
Existing electromagnetic shields are typically comprised of a metallic material to prevent the transmission of radio frequency electromagnetic signals. The shield is typically formed of a plate member suitable for positioning above a circuit component element (or entire circuit), and includes side flange portions extending downwardly therefrom to cover side portions of the circuit component element. In order to function properly, the shield must be electrically coupled to the electrical circuit over which the shield is positioned.
Because many electrical devices are packaged in ever-smaller housings, ever-smaller heat sink assemblies and electromagnetic shields are required. In many instances, the heat sink and the electromagnetic shield are combined in a single element. For example, portable transceivers, such as portable, cellular phones, are increasingly miniaturized to permit the transceivers to be of ever-smaller dimensions. A heat sink which further functions as an electromagnetic shield permits increased miniaturization of the portable transceiver.